1. Field of the Invention
The present invention relates to a storage system and a method for allocating storage area.
For example, in order to manage efficiently the rapidly increasing amounts of information in various organizations such as administrative organizations, enterprises, and universities, storage resources are shared between a plurality of computers. The SAN (Storage Area Network), for example, is known as such a system.
The SAN, for example, has a plurality of host computers (hereafter referred to as ‘hosts’), and a plurality of storage apparatuses. Data can be transferred between each host and storage apparatus based on, for example, a fiber channel protocol.
The storage apparatuses are also referred to as ‘disk array devices’ or ‘storage subsystems’ and the like, and are composed of a large number of physical storage devices disposed in an array. A storage apparatus can provide a plurality of storage areas based on, for example, a RAID (Redundant Array of Independent Disks). A logical volume (logical storage device) being a logical storage area is formed on the physical storage area of each disk drive.
Each host can conduct data I/O using the logical volumes allocated to itself. For example, application programs running on the host (hereafter referred to as ‘applications’) such as database management programs and the like employ data groups stored on the prescribed logical volumes to achieve the prescribed operations.
In a storage system which can provide a large number of logical volumes to each host, the desired logical volume can be selected and used. In contrast to these advantages, since there are too many possibilities for selection of logical volumes, the user is at a loss as to which logical volume to allocate to which application.
2. Description of the Related Art
A technology in which a management program for managing storage resources within the storage system from a single point is provided, and logical volumes are allocated to each host with this program, is disclosed in Japanese Patent Application Laid-open No. 2001-142648. In the technology disclosed in this patent document, when a new logical volume is required, each host notifies the management program of the necessary volume size and RAID configuration type. The management program selects a logical volume matching the request from the host, and allocates this selected logical volume to the host.
The management program disclosed in the afore-mentioned document receives a request from the host, and allocates a logical volume to that host. Allocation of volumes is therefore hidden from the user, and the user need not be aware of the type and number of physical storage devices.
However, in the conventional technology disclosed in the afore-mentioned document, the broad conditions related to the logical volume such as volume size and RAID configuration can be specified, however, detailed conditions such as position and access path of the physical device comprising the logical volume cannot be specified.
Therefore, when the practical method of use of the application is considered, there is an unresolved problem in that an optimum logical volume cannot be selected for the application. For example, it is desirable that database files and system files employed by the database management program be stored on differing physical storage devices, or on physical storage devices having differing access paths.
When database files and system files are stored on the same physical storage device, data I/O associated with creation of system files, and data I/O with database files, are conducted for the same storage device. Thus, storage device I/O conflict occurs, and response performance deteriorates.
Furthermore, in terms of reliability, important files such as system files are stored on a plurality of logical volumes and thus duplicated. In this case, also, it is desirable that duplicated files be stored on physically different storage devices.
Thus, the practical method of use, and the used content, of the files used by the application is understood by the application, and the method of use and the like differs with application type and the like.
However, in the conventional technology disclosed in the afore-mentioned document, selection of a logical volume in consideration of the method of use of the files by the application is not possible. Thus, with the conventional technology, a problem exists in that there is a possibility that a logical volume unsuitable in terms of reliability and performance will be selected, and a logical volume suitable for the application cannot be selected.